Refactor: ActiveStream::next function clean-up
Refactor: ActiveStream::next function clean-up

The ActiveStream::next function appears to have originally been
responsible for state machine transition, and contains a significant
amount of redundant code.  This has been removed.

Change-Id: I8597d741af4063d4ab8f54df49dddb7b471531e4
Reviewed-on: http://review.couchbase.org/74441
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>

membase/ep-engine,membase/ep-engine,membase/ep-engine,daverigby/kv_engine,daverigby/kv_engine,couchbase/ep-engine,membase/ep-engine,couchbase/ep-engine,daverigby/kv_engine,daverigby/kv_engine,couchbase/ep-engine,couchbase/ep-engine